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1. Field of the Invention
The present invention relates to radar receivers. More specifically, the present invention relates to multi-purpose filters used in high performance digital radar receivers.
2. Description of the Related Art
Sophisticated high performance military and commercial digital radar receivers detect and process signals in complicated environments that include broadband clutter, interference sources (intentional and unintentional), echoes, and receiver noise. These receivers perform some or all of the following functions: synthesize in-phase (I) and quadrature (Q) components from high-speed sampled signals, form video filters, notch DC components, decimate data, provide channel-to-channel equalization, perform digital range correlation, and provide interference cancellation.
Currently, these tasks are performed by Hilbert filters, digital video filters, equalization filters, discrete Fourier transform, filters, decimating filters, convolvers, correlators, and general purpose cascadable FIR filters implemented in commercial off-the-shelf hardware (COTS) and customized hardware in embedded systems.
Unfortunately, digital radar receivers implemented in accordance with conventional teachings often require several hundred signal processing chips. As a result, conventional digital radar receivers are typically heavy, bulky, and expensive to develop and manufacture. In addition, these receivers typically consume considerable power and generate much heat.
Hence, there is a need in the art for a unique receiver architecture that is highly flexible, scalable, and reconfigurable that can perform the numerous functions mentioned above. Also, during real time embedded applications, the architecture should be continually reconfigurable to quickly, easily and inexpensively handle changing requirements.
The need in the art is addressed by the signal processor of the present invention. Generally, the inventive signal processor includes a plurality of filters which are selectively interconnected to provide a variety of digital signal processing functions. In the illustrative embodiment, each filter is adapted to multiply input data by a coefficient. Specifically, each filter includes circuitry to multiply input data by coefficients to form digital filtering products and adders to accumulators the sum of the products. The coefficients are provided by a microprocessor to configure the logic to a particular function, such as a general purpose filter, a Hilbert filter, a finite impulse response filter, an equalizer, a beamforming network, a convolver, a correlator, or an application specific integrated circuit by way of example. When interconnected in accordance with the teachings provided herein, these circuits may be used to provide a digital receiver.
That is, a digital receiver, constructed in accordance with the present teachings would comprise a plurality of general purpose filters constructed in accordance with the present teachings. Each filter would have a plurality of filter banks, switching circuitry to interconnect the filter banks, and programmability provided by an external processor. The processor configures the filter banks, to provide a delay element, a first decimating filter and a first equalizer in a first channel of a first general purpose filter and a Hilbert transform, a second decimating filter and a second equalizer in a second channel of the first general purpose filter. A first range correlator is provided in a first channel of a second general purpose filter and a second range correlator is provided in a second channel of a second general purpose filter. The first channel of the first general purpose filter is connected to the first channel of the second general purpose filter and the second channel of the first general purpose filter is connected to the second channel of the second general purpose filter.
An external processor programs the general purpose filter to configure the filter banks to simultaneously provide the functions found in most digital receivers (Hilbert transforms, video filters, equalizers, range correlation, and general purpose video filters).
The versatile, flexible and reusable features of the inventive general purpose filter architecture allows analog and digital receivers to be built using a single chip type. Accordingly, the receivers are much smaller and lighter in weight than conventional systems and have lower associated power dissipation, thermal heating, and development and manufacturing cost.